Follow Path interpolation problem: numerical instability?
I recreated your example just to see that happens, although on my system, the "interesting" frames were different.

Path is a parametric curve, P(t). It is natural that the dP/dT = (P(t+dt) - P(t))/(dT) is not constant.  Blender is trying to find such a dT(i) for every i-th frame to make your point moving along the path in constant steps. And it fails sometimes.

This is happening because your path has a long segment (from y=0 to y=90), while your other segments are significantly shorter. You can try inserting more control points into the longest segment (just subdivide it a few times). This will increase the accuracy of derivative computations.  I usually keep my segments at equal lengths.

PS if you shorten the longest segment, the error will reduce dramatically